Refrigeration apparatus including compressor motor cooling means



Nov. 24, 1964 R. E. RAYNER 3,158,009

REFRIGERATION APPARATUS INCLUDING COMPRESSOR MOTQR COOLING MEANS Filed Jan. 23, 1963 2 Sheets-$heei l RAYMOND E. RAYNER INVENTOR. QM MM Nov. 242-, 1964 F2. E. RAYNER 3, 8, 09

REFRIGERATION APPARATUS INCLUDING COMPRESSOR MOTOR COOLING MEANS Filed Jan. 23, 1965 2 Sheets-$heet 2 @W/ZIW/V/AWL In RAYMOND E. RAYNER IN VEN TOR.

BY M M United States Patent 3,158,099 REFRHGERATEOII APPARATUS ENCLUDINQ COM- PRESSGR MUTGR COOLENG Ii EEANS Raymond E. Rayner, Colonia, Nah, assiguor to Worthington Corporation, Harrison, NJ a corporation of Delaware Filed Jan. 23, 19%, Ser. No. 253,481) 3 Claims. (Cl. 62-505) The invention relates to a refrigeration system. It relates more particularly to a system including an arrangement of components in which a vaporizable refrigerant is circulated, a part of the system being a compressor drive motor.

Refrigeration systems of the type contemplated embody as the prime mover a compressor delivering hot com pressed vaporous refrigerant. To provide continuously running efficiency it is desirable that the compressor drive motor be sufficiently cooled as to be unaffected by overloading or continuous operation. Drive motors are generally built for the stated purpose in such manner as to permit free circulation of air or gas across heated motor parts. More specifically, refrigeration system motors are generally constructed within a hermetic casing as to constitute a part of the closed system so that gaseous refrigerant vapor passes directly through the motor prior to being compressed.

Another and more efiicient construction embodies means employing a liquid coolant which evaporates upon contact with heated motor parts. This latter embodiment may take the form of a canned motor in which a liquid holding jacket surrounds the motor itself, or it may be of the type in which the motor components are submerged in a cooling liquid. Motors of both the canned and liquid immersed type find use in systems in which circulated refrigerant serves as the cooling medium. However, the mentioned motor designs embody certain disadvantages For example, motors into which gaseous refrigerant is drawn may be only slightly more efficient than air cooled types. A liquid cooled arrangement wherein submerging individual parts in a liquid bath, entails the disadvantage of creating fluid drag between the rotor and stator thus again minimizing running efficiency.

It is therefore an object of the present invention to provide an eflicient refrigeration system including a refrigerant cooled compressor drive motor.

A further objective is to provide a system which includes means for contacting heated motor components with a dispersed liquid refrigerant stream to utilize heat of evaporization for cooling motor parts.

A still further objective is to provide a system including a hermetic drive motor into which atomized liquid refrigerant is introduced to circulate through motor parts providing substantially uniform cooling of the respective coacting rotor and stator members.

It is another object to provide a liquid cooled compressor motor embodying a construction in which a high velocity liquid stream is introduced to a hermetic unit surrounding the motor to provide a continuous coolant path for uniformly cooling heated motor parts.

These and other similar objects of the invention will be come apparent to one skilled in the art from the following description made in conjunction with the drawings, in which:

In the drawings:

FIGURE 1 is a schematic illustration in cross-section of a refrigeration system of the type contemplated by the invention and includes a motor driven compressor having means for circulating liquid refrigerant to the motor as the cooling medium.

FIGURE 2 is a cross-sectional view on an enlarged scale of a hermetic motor embodying the invention.

arsases Patented Nov. 24, 1964 FIGURE 3 is a segmentary perspective view on an en larged scale of the motor rotor shown in FIGURES l and 2.

FIGURE 4 is a cross-sectional view on an enlarged scale of another hermetic motor embodying the invention.

FIGURE 5 is an enlarged cross-sectional view taken along line 5-5 of FIGURE 4.

FIGURE 6 is a variation of the system shown in FIG- URE 1 including a sub-cooling coil in the condenser element.

In brief, the objectives of the invention are achieved in the present refrigeration system by affording means whereby normally heated motor parts are placed in continuous heat exchange contact with droplets of vaporizable liquid refrigerant or, a gas borne stream of liquid refrigerant droplets. Thus, absorption of heat through evaporation of the refrigerant will effectuate a sustained cooling action. Uniformity of cooling is fostered by providing motor components with interconnected passages and chambers defining a path to encourage a continuous flow pattern in a direction from the point of entry of the liquid, to a low pressure exhaust port.

The apparatus constituting the instant system includes a compressor connected by conduit means to a condenser for delivering hot compressed vapors of a volatile refrigerant such as Rl1 or R-lZ. A high pressure receiver such as a condenser hot well or economizer chamber, holding both liquid and vaporous refrigerant at condenser head pressure, meters a stream of liquid to an evaporator through an expansion valve. The closed system is completed by conduit means communicating the evaporator vapor holding portion to the compressor suction for recirculating gaseous refrigerant.

As an adjunct of the system, the compressor is driven by a hermetically enclosed motor having a casing cornmunicated to receive at least a portion of the refrigerant flow. Conduit means communicates the saturated liquid holding receiver, to the motor casing inlet whereby a high velocity stream of liquid refrigerant in droplet form is in troduced to the casing interior for contacting motor parts. Both vaporized and excess liquid refrigerant are thereafter drawn from the casing and recirculated through a portion of the system at a pressure less than the receiver pressure.

Referring to the drawings, FIGURE 1 illustrates diagrammatically the system in general which comprises; a centrifugal compressor 1% having an inlet 11 connected by conduit 12 to the discharge 29 of an evaporator 14 for receiving and compressing vaporous refrigerant and forwarding the same through outlet 16 and conduit 17 t0 inlet 13 of condenser 13. Vapors are then condensed by contact with the cooling coil E into liquid form and forwarded through conduit 21 to a receiver 22.

Receiver 22 embodies a float chamber 23 holding a supply of saturated or slightly subcooled liquid refrigerant normally at condenser pressure. A float valve 24 disposed in chamber 23 regulates the level of contained liquid and meters a stream of refrigerant through conduit 26 to inlet 27 of evaporator 14. In the evaporator, a pool of the liquid immerses a fluid carrying coil 25 to extract heat from the circulating fluid. Refrigerant vapors then pass upward through a screen 28 to the evaporator outlet 29 from which conduit 12 redirects the vapors to the corn pressor inlet.

Cooling of the compressor drive motor 31 is accomplished by injecting a high velocity stream of saturated liquid refrigerant at substantially condenser pressure into hermetic casing 32 enclos'mg the motor. To this purpose, conduit means 33 communicates the lower, liquid holding portion of the high pressure receiver 22 carrying a stream of the saturated or slightly subcooled refrigerant to the inlet side of casing 32. A second conduit 34 connected to the lower or sump portion of casing 32 recieves re m r"! frigerant in both liquid and vapor phase for evacuating the same from the casing enclosure.

An oil cooler including a shell 36 is communicated through conduit 34 to the casing. An oil carrying coil 37 supported in the casing circulates lubricant from the refrigerant system or from a similar source for extracting heat therefrom. Thus, liquid and vaporous refrigerant passing across the surface of coil 37 is further heated or vaporized and directed to the vapor holding portion of the evaporator by way of conduit 38.

Conduit 33 communicates motor casing 32 with a pressurized refrigerant source and may include flow regulating means such as a valve 39. This valve may be solenoid operated to adjust liquid injection or is automatically responsive to a condition in the motor to adjust the flow. Valve 39 may be eliminated completely or else positioned as close as possible to the motor inlet since passage of the pressurized liquid through the constricted valve will result in flashing at the downstream side.

Where it is necessary to overcome a static head, as where the motor 31 is positioned substantially higher than receiver 22, a pump not presently shown in the drawings may be connected in line 33. Other flow control means may also be incorporated into the circuit to regulate refrigerant flow through casing 32 by providing a valve means 41 downstream of casing 32 in conduit 34 regulating fiuid flow from the motor casing.

Referring to FIGURE 2, hermetic motor 31 comprises in general a stator element 51 supported within casing 32 by longitudinally extending ribs 52 to define channels 53 between the stator peripheral surface and adjacent casing walls. In accordance with standard motor construction practice, a plurality of radial openings 54 traverse the stator providing passage for cooling fluid from internal portions. End turns 48 and 49 of the stator energizing windings, extend laterally from the stator and into the respective ends of the casing enclosure.

There is thus defined by pasages 54 and channel 53, a path for conducting a continuous fluid refrigerant stream. While the ribs 52 are mentioned as extending longitudinally of the motor, these members may be embodied in thin ring-like elements supportably disposed about the stator and having perforations or other openings permitting fluid flow of refrigerant along the stator outer surface.

Stator 51 is positioned approximately centrally of the casing defining opposed end chambers 56 and 57 respectively. At least one of the end chambers, as for example 56, is provided with means for introducing an atomized stream of liquid refrigerant to the casing enclosure. Chamber 57 includes a drain 59 to lead off liquid not vaporized within the enclosure, and also to remove refrigerant vapors.

The rotor 61, also positioned within casing 32, following standard motor design includes a'central shaft 62 having end bearings 63 and 64 journale'd at the casing wall to rotatably support the rotor in the central opening of stator 51. At least one shaft end traverses a wall of the casing as at the end adjacent chamber 57. A labyrinth or other similar type seal carried about the shaft at the casing wall provides a pressure resistant fluid seal to retain the normally pressurized atmosphere within the motor casing.

While it is not intended to impose unnecessary limitations on the scope of the invention, the present cooling system is particularly adapted for use in large commercial units typified by a chiller apparatus having sufficient capacity as to require a 100 to 1000 HP. drive motor.

Multi-pole motors of this magnitude are generally manufactured with a rotor construction which embodies a plurality of ring segments carried on the shaft and assembled to define a mounting frame for rotor coils or bars. The latter are so arranged as to be spaced inwardly of the stator forming a clearance gap therebetween. An embodiment of the rotor ring segments as shown in FIGURE 3 comprises an inner bushing 42 which may be segmented, and include rim 43 adapted to engage corresponding parts of adjacently positioned segments. The elements are so fastened as to form a unitary spiderlike structure. Thus assembled the segments form an elongated annular chamber 44 about the motor shaft 62. Barlike spoke elements 46 radiate outwardly from the inner bushing in support of the rim section, the bushing 42 is carried on the shaft 62 as by a key or similar means for rotation therewith.

Referring to FIGURE 2, a means by which coolant is introduced to the motor end chamber 56 includes an arrangement particularly adapted to overcome any tendency for creation of static areas Within the motor enclosure. An eflicient flow pattern for the coolant stream is achieved by providing a manifold 68 having a fluid tight coupling 69, extending through and fastened to the motor casing wall and in communication with conduit 55. The manifold includes a plurality of injectors generally designated 67, having discharge ends either constricted or provided with nozzles for delivering liquid refrigerant therefrom in an atomized stream of liquid droplets.

To assure uniform cooling and a relatively equalized flow, the atomized streams are directed against the motor end face and also into central chamber 44. As shown in FIGURE 2, at least one stream is directed into outer annular passage 52. A second stream enters the annular gap between rotor and stator surfaces. The third atomized stream enters the rotating central chamber 44. While presently shown as individual nozzle members, the respective injectors may be circularly disposed about the end chamber in such manner as to simultaneously feed several streams of atomized liquid into and against the motor end passages.

High speed rotation of chamber 44 together with existing pressure difference between chambers 56 and 57 urges the atomized streams into a generally spiral configuration. Referring to FIGURE 3, vanes or other rotating inductors such as spokes 46, may be shaped or conformed to induce the spiralling stream toward the chamber discharge end to provide an even distribution of atomized fluid.

Centrifugal force acting on the minute liquid droplets carries the latter into the relatively wide mouth at the inner end of radial passages 72 formed in the rotor in substantial alignment with pasages 54 in the stator. An end plate or closure means 74, shown in FIGURE 2, carried on the rotor at the discharge end provides a restricted opening as required in chamber 44 thus limiting tlzjhe flow of refrigerant passed directly into the end cham- Referring to FIGURE 1 showing the entire system, operation will be described using refrigerant R-12 as the circulating medium. Vapors received from the evaporator 14 are introduced to inlet 11 of compressor 10 having a high speed impeller. At the compressor outlet 16, hot compressed vaporous refrigerant in superheated condition is conducted through conduit 17 into the upper vapor holding portion of condenser 18. Refrigerant after being condensed, accumulates in receiver 22 normally holding saturated or slightly subcooled liquid under condenser head pressure. The major portion of accumulated liquid is metered through float valve 24 into conduit 26 for introduction to the evaporator. A second or lesser flow of liquid will be conducted into conduit 33 through control valve 39 if such is required, thence through conduit 55 to the motor casing 32. This secondary liquid flow is solely for cooling purposes and on a volume basis will be contingent on the physical size of the motor, the amount of cooling required, and also upon the capacity of the refrigerating system.

It has been found that with proper cooling of the compressor motor through circulation and evaporation of liquid refrigerant droplets, the motor dimensions can be substantially reduced to approximately one half the.

original size. That is, for a system ordinarily requiring about a 1000 H.P. motor, with proper cooling as herein described, the motor mass can be reduced to the equivalent of a 500 H.P. unit. In order to assure an adequate flow of refrigerant into and through the motor, the incoming stream is so adjusted as to be slightly in excess of that which is actually required for cooling purposes. A suitable flow rate is determined by increasing the rate such that all the liquid droplets are not vaporized even though the motor is adequately cooled, but rather a portion thereof reaches the downstream chamber 57 while still in liquid form. At inlet chamber 56, as previously mentioned the atomized refrigerant streams are directed into the chamber toward and onto motor parts. These streams enter the various radial and transverse motor passages in order that a flow pattern might be established which provides substantially equalized cooling to all parts of the motor interior.

Thus, the greatest flow of atomized liquid will normally be directed to the central chamber 44 and thence urged by centrifugal force into radially aligned passages to both the rotor and the stator; By providing an adequate stream, only a portion thereof will be vaporized by contact with hot motor surfaces while still permitting a substantial flow of droplets. Thus the cooling stream established is essentially one of liquid refrigerant droplets being borne along by vaporized refrigerant gas.

At discharge chamber 57, accumulated vaporous and liquid refrigerant gravitates toward the bottom portion of casing 32 and is conducted thence into the oil intercooler 36 or returned to evaporator 14 through conduit 38.

The continuous flow pattern through the motor is maintained not only by virtue of the amount of liquid introduced at the motor inlet end but also by control of the pressure maintained downstream of the motor casing through outlet valve 41. Thus, the pressure differential across the motor inlet and motor outlet may be automatically or manually controlled to assure a proper cooling flow to the motor parts.

FIGURE 4 illustrates an alternate embodiment of the invention in which a smaller motor than that previously discussed may be effectively cooled. As shown, motor 80 comprises basically a stator 81 and a rotor 82 surrounded by hermetic casing 83. While the general disposition and cooperation of basic elements in the present motor is substantially identical with what has been disclosed in the embodiment of FIGURES 1 and 2, a primary difference is in the rotor construction.

Rotor 8.2 consists of an elongated shaft 84- carrying a solid, packed laminated core. The core is provided with outwardly extending passages 85 disposed in alignment with radial passages 86 formed in the stator. The respective shaft ends are journaled at the casing 83 to permit free rotation of the rotor within the stator.

As shown in enlarged FIGURE 5, shaft 84 is provided at its outer surface with a plurality of longitudinally extending channels or slots 87 which are peripherally disposed about the shaft and which terminate beyond the respective core end faces. The slots may be formed directly into the shaft surface or alternatively be defined by longitudinally disposed ribs.

Injector 88 extends through one end wall of the casing and is formed to direct a high velocity stream of liquid against the shaft surface to permit entry of a liquid droplet stream into the respective shaft grooves 87. These grooves conduct the stream of droplets along the respective shaft slots from which said droplets are propelled by centrifugal force into aligned radial passages 85 and 86. A constricting ring 89 or a similar device may be disposed at the downstream side of the rotor shaft to prevent the coolant stream from passing directly through the rotor and out into the adjacent casing end chamber. The normal path of liquid refrigerant through the motor will thus be from the radial passages, into the annular passage about the stator, thence into the discharge chamber of the motor casing.

Further, while the refrigerants suggested for use in the system include R11 and R12, it is understood that other similar vaporizable materials known to one skilled in the art may be substituted.

FIGURE 6 illustrates an alternate embodiment of the invention similar to the system shown in FIGURE 1. Here, however, a flow of liquid refrigerant is drawn from the receiver 22 through line 33'. Coil 25' positioned in the condenser is connected to line 33' such that saturated refrigerant might be sub-cooled prior to being carried through conduit 33 to the motor casing.

What is provided by the present system is an arrange ment to fully utilize heat of vaporization of the refrigerant to uniformly cool motor parts. The desired cooling pattern is effected in part by formation of a gas borne stream of particles. Thus the vaporous phase liquid droplets are carried into contact with heated surfaces whereby further vaporization is effected.

The disclosed system therefor provides economic advantages in both cost and motor maintenance over both vapor cooling and liquid immersed systems.

It is understood that while the above description is directed to a particular embodiment of refrigeration system, it is not intended to so limit the scope of the invention. Certain modifications and changes might be made by one skilled in the art altering the structural features, particularly of the cooled motor, without departing from the spirit and scope of the invention.

What is claimed is:

1. In a closed refrigeration system circulating volatile refrigerant, a compressor including a suction inlet and having a drive motor connected thereto, a condenser, an evaporator holding liquid and vaporous refrigerant at a pressure less than condenser pressure, said evaporator being connected to receive condensate from the condenser and to deliver vaporous refrigerant to the compresssor suction inlet, a high pressure receiver connected downstream of the condenser holding saturated liquid refrigerant under substantially condenser head pressure;

(a) said drive motor connected to the compressor having a hermetic casing including inlet and outlet means,

(b) first conduit means communicating the high pressure receiver to the hermetic casing inlet means carrying a saturated liquid refrigerant suearn for introduction to the hermetic casing at substantially condenser pressure,

(c) injection means connected to said first conduit means and having a liquid atomizing nozzle positioned in the hermetic casing forming the saturated liquid into a stream of dispersed liquid droplets,

(d) said drive motor including a rotor having an axial shaft supported in the hermetic casing,

(9) means in said rotor forming a central chamber extending longitudinally of the shaft,

(f) passage means disposed in said rotor in communication with said central chamber,

(g) said injection means being disposed to direct atomized refrigerant into said central chamber,

(11) and means carried in said central chamber and rotatable therewith, urging the refrigerant stream therethrough.

2. In a system substantially as defined in claim 1 wherein said means carried in said central chamber and rotatable therewith includes a plurality of radial vanes supportably holding the shaft in the rotor.

3. In a closed refrigeration system circulating volatile refrigerant, a compressor including a suction inlet and having a drive motor connected thereto, a condenser, an evaporator holding liquid and vaporous refrigerant at a pressure less than condenser pressure, said evaporator being connected to receive condensate from the condenser and to deliver vaporous refrigerant to the compressor suction inlet, a high pressure receiver connected downstream of the condenser holding saturated liquid refrigerantunder substantially condenser head pressure;

(a) said drive motor connected to the compressor having a hermetic casing including inlet and outlet means,

(b) first conduit means communicating the high pressure receiver to the hermetic casing inlet means carrying asaturated liquid refrigerant stream for introduction to the hermetic casing at substantially condenser pressure,

(c) injection means connected to said first conduit means and having a'liquid atomizing nozzle positioned in the hermetic casing forming the saturated liquid into a stream of dispersed liquid droplets,

((1) said drive motor including a rotor having an axial shaft supported in the hermetic casing,

(2) said shaft having longitudinally extending grooves formed in the periphery thereof and terminating outwardly adjacent ends of said rotor, defining passages through the latter,

(f) said injection means having an outlet positioned to 2 direct atomized refrigerant against said shaft and into said longitudinally extending grooves and,

(g) passages formed in said rotor and being communicated with said longitudinally extending grooves for carrying refrigerant therethrough to cool said motor.

References Cited by the Examiner UNITED STATES PATENTS 2,776,542 1/57 Cooper 62-505 2,793,506 5/57 Moody 62505 2,891,391 6/59 'Kocher 62-505 3,088,042 4/63 Robinson 62- 505 1 FOREIGN PATENTS 863,964 3/61 Great Britain. 863,955 3/61 Great Britain.

References Jilted by the Applicant UNITED STATES PATENTS Re. 24,802 3/60 Kocher. 1,121,014 12/14 Hobart. 2,184,285 12/36 odling. 2,746,269 5/56 Moody. 2,768,511 10/56 Moody. 2,986,905 6/61 Kocher et a1.

, ROBERT A. OLEARY, Primary Examiner.

MEYER PERLIN, Examiner. 

1. IN A CLOSED REFRIGERATION SYSTEM CIRCULATING VOLATILE REFRIGERANT, A COMPRESSOR INCLUDING A SUCTION INLET AND HAVING A DRIVE MOTOR CONNECTED THERETO, A CONDENSER, AN EVAPORATOR HOLDING LIQUID AND VAPOROUS REFRIGERANT AT A PRESSURE LESS THAN CONDENSER PRESSURE, SAID EVAPORATOR BEING CONNECTED TO RECEIVE CONDENSATE FROM THE CONDENSER AND TO DELIVER VAPOROUS REFRIGERANT TO THE COMPRESSOR SUCTION INLET, A HIGH PRESSURE RECEIVER CONNECTED DOWNSTREAM OF THE CONDENSER HOLDING SATURATED LIQUID REFRIGERANT UNDER SUBSTANTIALLY CONDENSER HEAD PRESSURE; (A) SAID DRIVE MOTOR CONNECTED TO THE COMPRESSOR HAVING A HERMETIC CASING INCLUDING INLET AND OUTLET MEANS, (B) FIRST CONDUIT MEANS COMMUNICATING THE HIGH PRESSURE RECEIVER TO THE HERMETIC CASING INLET MEANS CARRYING A SATURATED LIQUID REFRIGERANT STREAM FOR INTRODUCTION TO THE HERMETIC CASING AT SUBSTANTIALLY CONDENSER PRESSURE, (C) INJECTION MEANS CONNECTED TO SAID FIRST CONDUIT MEANS AND HAVING A LIQUID ATOMIZING NOZZLE POSITIONED IN THE HERMETIC CASING FORMING THE SATURATED LIQUID INTO A STREAM OF DISPERSED LIQUID DROPLETS, (D) SAID DRIVE MOTOR INCLUDING A ROTOR HAVING AN AXIAL SHAFT SUPPORTED IN THE HERMETIC CASING, (E) MEANS IN SAID ROTOR FORMING A CENTRAL CHAMBER EXTENDING LONGITUDINALLY OF THE SHAFT, (F) PASSAGE MEANS DISPOSED IN SAID ROTOR IN COMMUNICATION WITH SAID CENTRAL CHAMBER, (G) SAID INJECTION MEANS BEING DISPOSED TO DIRECT ATOMIZED REFRIGERANT INTO SAID CENTRAL CHAMBER, (H) AND MEANS CARRIED IN SAID CENTRAL CHAMBER AND ROTATABLE THEREWITH, URGING THE REFRIGERANT STREAM THERETHROUGH. 